My Roku device suddenly either can't find the wifi signal at all or only finds a very weak signal that hangs around for about 30 seconds before disconnecting. It was working fine and then randomly just started doing this in the middle of the show. Restarting the router does nothing, restarting the Roku does nothing. My phone gets a perfect signal sitting next to the Roku. Laptops and gaming systems all fine. Only the Roku has a problem. Any ideas?